Preparation of C/C Composites by CVI with Multi-factor Coupling Physical Fields and Deposition Mechanism

The carbon felt as porous matrix, liquefied petroleum gas (LPG) as carbon source, by installing electric layers in the felt forming the grads of temperature and electromagnetism, C/C composites were fabricated by chemical vapor infiltration (CVI) with multi-factor coupling physical fields. The textures of pyrolytic carbon were observed by a polarization microscope(PLM), and the graphitization degree and minicrystal size of the C/C composites were analized by XRD. All samples were fabricated at one cycle. The densities of the matrix were measured by online coupling with resistance.At last,the mechanism of multi-factor coupling physical fields and deposition of carbon was discussed. The results show that, with multi-factor coupling physical fields, the rate of deposition of pyrolytic carbon can be improved greatly, and when deposited for 20h, C/C composites with densities of more than 1.7g/cm3 will be obtained. Through optimizing the infiltration conditions, some microstructures of pyrolytic carbon can be obtained ,range from rough laminar,smooth laminar, and banded structure. The graphitization degree of the rough laminar can be over 77% after heat treatment at 2300℃ for 2h.